Presently, sodium and potassium compounds are often included in flux ingredients for controlling arc stability. Arc stability is critical for alternating current (AC) operability, low direct current (DC) operability and out-of-position welding. Sodium and potassium compounds have long been used to stabilize welding arcs to increase welding operability. A problem with welding fluxes containing sodium and potassium allegedly is that they promote the formation of hexavalent chromium fumes during welding in the presence of chromium or chromium compounds. Hexavalent chromium fumes are not desirable and are preferably maintained at as low of a level as possible.
Others have attempted to solve this problem by eliminating sodium and potassium compounds from welding flux and binder ingredients. The technique has successfully limited the amount of hexavalent chromium formation, but at a great sacrifice to welding operability. These sodium- and potassium-free weld rods have less than desirable arc stability resulting in poor out-of-position welding, poor AC operability and poor low DC current operability. Bentonite, talc and silicates of sodium, potassium, and lithium advantageously are used to make electrodes that can be baked without cracking the coating. Once baked, electrodes must have an adequate coating for toughness to survive shipping. Electrodes free of potassium and sodium silicates typically have very poor toughness.
Hydroxyethylcellulose and other similar organic can be relied on to give a tough coating largely free of sodium and potassium provided that they are not baked out above 204-246.degree. C. Exposure to temperatures above this will break down these organic compounds leaving the coating without strength. Baking at 232-260.degree. C. for toughness will typically results in a coating with greater than 0.6% moisture and porosity in welds.
In addition to weld stability, the flux must also be capable of producing a slag having several properties. The slag must quickly solidify to provide support for the weld and to hold the slag in place when welding on sloped surfaces and especially on overhead surfaces. In addition, the slag must be easily cleaned or removed from the surface. Fluoride compounds are added to the weld flux to add proper fluidity to the slag and clean welding area. A common fluxing agent is cryolite (Na.sub.3 AlF.sub.6) which adds fluidity to the weld, but cryolite also introduces sodium which promotes the formation of hexavalent chromium fumes. Thus, it is desirable to eliminate cryolite or limit use of cryolite to as low of levels as possible.
Sulfur and phosphorus, commonly known as tramp elements, are detrimental to weld deposit properties. These tramp elements often are introduced into a weld from impurities in flux ingredients. Magnesium and manganese are often used to limit harmful effects of sulfur in the weld. Phosphorus is typically controlled by stringent limitation of phosphorus in the welding electrode. Control of these tramp elements is essential for producing welds having acceptable properties.
It is an object of the invention to produce a stainless steel welding electrode with low hexavalent chromium fuming and good arc stability for improved welding characteristics.
It is a further object of the invention to produce a weld that solidifies quickly and is easily cleaned.
It is a further object of the invention to limit the amount of tramp elements in the weld.